The Skeletal System

Human Biology and Health

Chapter 1, Section 2

What is the SKELETON?

• The framework of the body made up of all the bones in the body

• Determines the shape of the body• Comes from a Greek word meaning “a

dried body”

5 Major Functions of the Skeletal System

1. Provide shape and support

2. Enable movement

3. Protect the organs

4. Produce blood cells

5. Store minerals and other materials until needed by the body

Provide shape and support

• BACKBONE (vertebral column) is the center of the skeleton

• Made of 26 small bones call VERTEBRAE (singular vertebra)

Provide shape and support

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Notice all bones in the skeleton are in some way connected to this column.

CHECK POINT

Q. Why is the vertebral column considered the center of the skeleton?

A. All the bones in the skeleton are in some way connected to the backbone.

Enable movement

• The skeleton allows you to move• Most of the bones are associated with

muscles• The muscles pull on the bones to make

the body move

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What is a JOINT?

• A place where two bones come together• Allows bones to move in different ways

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Two Types of Joints

1. IMMOVABLE JOINTS- allow little or no movement

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Two Types of Joints

2.MOVABLE JOINTS- Make up most of the joints in

the body- Allow the body to make a wide

range of movements- Held together by strong

connective tissue call LIGAMENTS

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Two Types of Joints

- CARTILAGE is a more flexible type of connective tissue that covers the ends of bones to keep them from rubbing against each other

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Two Types of Joints

CHECK POINT

Q. How are movable joints held together?

A. With strong connective tissue called ligaments

Why didn't the skeleton cross the road?

It didn't have the guts!

What do you call a skeleton who won't work?

Lazy bones!

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Hinge Joint – allows forward and backward motion

Example: knee and elbow

Types of Movable Joints

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Ball-and Socket Joint – allows the greatest range of motion

Example: shoulder and hips

Types of Movable Joints

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Pivot Joint – allows one bone to rotate around another

Example: neck

Types of Movable Joints

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Gliding Joint – allows one bone to slide over another

Example: wrist and ankle

Types of Movable Joints

Protect the organs

• Bones protect most organs in the body

• Example: breastbone and ribs form a cage around the heart and lungs

Produce blood cells

• Blood cells are produced in marrow located in long bones like the legs and arms

• The process is known as hematopoiesis• Produces approximately 500 billion blood

cells per day

Store minerals and other materials until needed by the body

• Stores calcium, phosphorus, and other minerals

• Releases small amounts into the blood when needed

CHECK POINT

Q. What part of the bone produces blood cells?

A. The marrow.

What smells the best at dinner?

Your nose!

Why is your nose in the middle of your face?

Because it is the scenter!

Bone Structure

• Bones are complex living structures that undergo growth and development

Bone Structure

• A thin, tough membrane covers all of the bone except the ends

• Blood vessels and nerves enter and leave the bone through the outer membrane

Bone Structure

Compact bone•layer just below the membrane•Hard and dense but not solid•Contains small canals for blood vessels and nerves

Bone Structure

Spongy bone•Layer just below the compact bone•Has small spaces within it•Can also be found at the end of bones•Lightweight but strong

Bone Structure

Marrow•Soft connective tissue•Two types: red and yellow•Red marrow – produces blood cells•Yellow marrow – stores fat for energy reserve

CHECK POINT

Q. Name three levels in bone

CHECK POINT

Q. What does red marrow do?

A. Produces blood cells.

CHECK POINT

Q. What does yellow marrow do?

A. Stores fat for energy.

THINK DEEPER

Q. Short bones, like those in the fingers are mostly spongy bone. Why do long bones have more compact bone?

A. Long bones have compact bone because they are used to support the body and need to be stronger.

Taking Care of Your Bones

• Dieto Eat well-balanced diet

• Exerciseo Weight-bearing activities help bones

grow stronger and denser

Osteoporosis

• A condition in which the body’s bones become weak and break easily